This invention relates to a laser processing apparatus and, more particularly, to a laser processing apparatus with which high quality and efficient welding of metals can be obtained.
In the process of welding metals by irradiation of a pulse laser beam, the waveform of the pulse laser beam has great influence upon the mechanical strength of the weld and the finish shape of the weld surface. Thus, for obtaining better welding, it is very important to form a waveform that is suited to the welding.
With the prior art laser processing apparatus, however, it has been in practice to generate a rectangular waveform laser pulse output through optical pumping of a laser rod with rectangular waveform pumping light from a flash lamp which is driven by a pulse power supply with an on-off control element such as switching thyristor. In this process, molten metal generated by irradiation of above-mentioned rectangular waveform laser output is cooled down suddenly by a rapid stop of laser power irradiation while it is still unstable within the weld 10. Therefore, as shown in FIG. 1 blow holes 12 are liable to be created within the weldment. Also, the superficial portion of the weld is partly spattered to result in the formation of extreme irregularities. These lead to the reduction of the mechanical strength or deterioration of the finish of the weld.
Also, there is an apparatus which does welding by the slowing falling laser pulse output power which is emitted from a rod pumped by a flash lamp driven by a charging and discharging capacitor. With this type of apparatus, the workpiece metals are cooled after they are sufficiently stabilized, so that it is possible to obtain high quality welding. In this apparatus, the capacitor is completely discharged until it has no charge before it is charged again for the next discharging operation. Therefore, it has been difficult to repeatedly generate pulses at a high repetition rate, so that the processing throughput has been low.